Electric cable or other insulated conductor



March 2, 1943. F. w. TOMLINSON ETAL 2,312,506

'ELECTRIC CABLE OR OTHER INSULATED CONDUCTOR Filed June 20, 1959 INSULATION 26 44 4/574 SHE/Th 4U. 01

ME 714 SHE/9734 17v vs 7-088 fiid'fbmzz/izo'an 33 61/14, Eeckeii irroxwvsy Patented Mar. 2, 1943 UNITED STATES PATENT OFFICE ELECTRIC CABLE OR OTHER INSULATED CONDUCTOR Frederick William Tomlinson and Charles Murray Beckett, Newcastle-on-Tyne, England, assignors to Socit Alsacienne dc Constructions Mcaniques, Clichy, France, a body corporate of France Application June 20, 1939, Serial No. 280,184 In Great Britain June 20, 1938 Claims.

' is inserted together with the conducting core or cores into a metal sheath and the work-piece so formed is subjected to a drawing or other metallurgical treatment to break down the insulating blocks into the form of a homogeneous powder and to bring the cable to its final dimensions.

In a cable or other insulated conductor according to the present invention at least oneof the metal parts (comprising the core or cores and the sheath) is furnished with a layer of duetile material difierent from that of the part to which it is applied. Intimate contact between. the layer and the part to which it is applied is preferably ensured by a drawing or other metallurgical treatment which may be constituted wholly by the treatment employed 'for bringing the work-piece to its final dimensions, or may consist wholly or in part of a separate treatment.

The material of which the layer is composed may vary and may for instance be chosen to suit the purpose to which the finished cable or other insulated conductor is to be applied.

Thus, when a cable of the type to which the invention relates is employed under conditions which may tend to cause scaling and/or corrosion of the metal (usually copper) employed for the core and sheath, for example in cases of exposure to considerable heating or to chemically charged atmospheres, as in internal connections of electric cooking appliances, or dye works or battery rooms, not only the sheath but also the exposed ends of the core or cores are liable to be impaired. The materials which will to be made of copper or other good conducting metal and yet to be protected by means of a relatively thin layer, for example of heat and/or corrosion resisting alloy, such for example as aluminium brass, or aluminium bronze, or nickel alloys, or tin, or lead, or alloys of tin or lead.

With the above and other objects in view which will become apparent from the following detailed description the invention is shown in the drawing in which:

Figure l is a cross sectional view of one modification;

Figure 2 is a cross sectional view of another modification; I

Figure 3 is a cross sectional view. of a still further modification of the invention;

Figure 4 is a cross sectional view of a still further modification;

Figure 5 is a longitudinal sectional view of a cable end; and

Figure 6 is a longitudinal sectional view of a modified construction for a cable end.

Referring to the drawing, in which like reference characters are used throughout the various figures to indicate similar parts, the modification shown in Figure 1 shows a copper core 5 embedded in the pulverulent insulation 6. This insulation may be formed for example by preformed blocks of magnesia furnished with passages to' receive the cores. The core 5 is generally of copper and the insulation 6 and the core 5 is arrangedmithin a copper sheath 1. The copper sheath 1, which together with the core I and insulation 6 constitutes a work-piece is inserted into a tube 8 which may be of aluminium brass alloy, for example that known under the registered trade mark "Alumbro having approximately 76% copper, 22% zinc and 2% aluminium.

There is provided just sufficient clearness to permit entry of the sheath insulation and the work-piece as a whole is then subjected to mechanical working, for example by drawing through a die, so that as the work-piece is drawn down the tube surrounding the core and the sheath is firmly closed into intimate contact with the sheath. Several of such drawing operations may be efiected with or without an intermediate annealing stage or stages. The exposed sheath therefore is fully protected against scaling or corrosion except for the small annular area at the exposed end of the copper sheath. The core 5 being. embedded in the insulation is also protected and the exposed ends 01 the copper sheath and core may be covered by a flux of a soda lead silicate composition.

Jigure or 6.

A protective layer on the outside of the cable enclosure for this purpose is provided for the cable end. g

The exposed end of the copper core or cores may be coated with a soft flux of a soda lead silicate composition 9 as shown in Figure 5 applied in a melted condition. This coating preferably extends also over the exposed end of the insulation and the copper sheath 1.

However a terminal connection such as shown in Figure 6 may be used. In this modification terminal leads III of a suitable metal, which is not subject to scaling orcorroslon are attached to the ends of the cores II and the joints ii are enclosed within a hollow bushing 13 containing a plug' 14 provided with separate passages 85 through which the leads l0 pass. The remaining space within the bushing is filled with a molten glazing flux l6 which extends over the end of thecable'insulation i1, sheath i8 and protecting tube is and between the copper cores ll connected to'the leads within the bushing.

The glazing flux when employed as above described not only .acts as an insulating medium and as a hermetic seal for the magnesia insulation, but also protects the copperparts, which would be otherwise exposed, against oxidizing air.

A protective layer on the outside of the sheath alone may also sufllce in other instances where, for example, mechanical rather than. corrosionresisting protection is required, and in such instances the material of the layer would be chosen more especially for its mechanical properties,

-e. vg., hardness. In this respect the aluminium brass alloy referred to is not only suitable for protection against corrosion, erosion and oxidation or.scaling at high temperatures but combines withthese properties a ductility which is not appreciably less than that of copper. Morethe insulation of the cable or. other insulated conductor a pulverulent material which is sumciently hard to cause damage to the core and/or sheath during the drawing or other metallurgical process. The invention enables this difllculty to be overcome by the use on the core or cores and the inner surface of the sheath of a protective skin or layer of suitably hard material.

.For example,,as shown in Figure 3 the copper core 25,- or each copper core when there is a plurality. of them, is inserted in a metal tube I 2.5 which is somewhat harder than copper, for example one of -the alloys above referred to, nickel chromium and aluminium-bronze alloys having a somewhat greater mechanical resistance than aluminium brass. Each core with its protective tube 26 is embedded in the pulverulent insulation 21, for example apertured pre-Zormed blocks as described, and the blocks containing the cores are inserted in a further protective tube 28 preferably of the same material as that surrounding the core or cores. The protective tube. 28 containing the insulation and cores is then inserted into a copperv sheath 2!! and the workpiece so formed is subjected to one or more mechanical working stages, with or without an in- In'this construction one of the cores 3| is proalloyand may tend to reduce the flexibility of the cable, this difllculty may be overcome by reduc ing the thickness of the protective tube or layer 7 applied.

Another modification is shown in Figure 2 wherein the core "is inserted into a tube II of the aluminium brass alloy and the core 20 with 'its surrounding tube It is embedded in the imiverulent insulation 22. The core, tube and in'sulation is arranged within a,v copper sheath 23- and these elements are inserted into a tube 24 of the aluminium brass alloy. The work-piece so constituted is thensubiected to mechanical working in the same manner as described with "reference to the modiilcationshown in Figure 1.

In this instance also the exposed sheath and the core or cores where they emerge at the ends of the cable are fully protected against scaling or.

corrosion except for the small annular areas at it is desirable is use-for is- In certain vided with athin skin or layer of material 32 which differs in appearance from that of they metal of the cores 3|. This layer 32 may'at the same time have'one or more of the protective properties above referred to. For example, ac-' cording to one method, one of the cores SI of a twin-core cable is coated with pure tin and the cores then embedded in the pulverulentinsulation 33 within the outer metal sheath 34. The.

work-piece thus formed is subjected to-one or more mechanical working stages, with or without an intermediate annealing stage or stages, so that the sheath. ation and cores are brought to the desired final dimensions; The tinned surface applied to one core retains its'separate identity throughout the mechanical working so that the cores of the finished cable are readily dis-' tinguishable at any cross-section in the length off the cable.

It will be understood-sthatinstead of applying the protective or distinguishing skin ori layer to .a core by the drawing process orme workpiece,"

the core'may be inserted in a tube'oi'the protective or distinguishing material and'the two parts subjected to a drawing or other metallurgical treatment so as to bring them into intimate contact before they are embedded. inthe pulverulent insulation.- Alternatively. the skin or layer maybe applied either to the core or to the' sheath in the form or a coating, for example by dipping or spraying. or by electro-deposition. It will that the methods above described are given-by wayof example only and f that the methods adopted in practice. as-

the materials eiiployed. will be chosen to suit requirements. For example,'the material em pioyed as the protective layer will be selected-to to secure by Letters Patent is:

suit the conditions under which the cable is to be used, though reasons of economy will not always permit the use of the most suitable material, e. g., silver in some chemical works, in which cases a somewhat cheaper though slightly less efiective material will be employed. Further, in cases where the skin or layer is intended solely for protection against corrosion the layer may be the exposed area isnot only small but does not constitute a vital part.

What we claim as our invention and desire 1. An insulated electric conductor comprising at least one conducting core, a surrounding metallic sheath, pulverulent mineral insulation separating the core from the sheath, and a layer of ductile material appliedto the surface of at least i one of the metal parts, such ductile material being harder than the metal of the part to which it is applied and being airtight and encircling all the exterior of the metal part covered.

2. An insulated electric conductor comprising at least one conducting core, a surrounding metallic sheath, pulverulent mineral insulation separating the core from the sheath, and a layer of ductile material applied to the surface of at least one of the metal parts, such ductile material being resistant to heat and to corrosion and being harder than the metal of the part to which it is applied and being airtight and encircling all .the exterior of the metal part covered.

3. An insulated electric conductor comprising at least one conducting core, a surrounding metallic sheath, pulverulent mineral insulation separating the core from the sheath, and a layer of ductile material applied both to the inner surface of the sheath and to the surface of the core, such ductile material being harder than the metals of the sheath and the core and being airtight.

4., An insulated electric conductor comprising at least one conducting core, a surrounding metallic sheath, pulverulent mineral insulation separating the core from the sheath, and a layer of ductile heat-resisting and corrosion-resisting material applied both to the surface of the core and to the inner and outer surfaces of the sheath, such ductile material being harder than the metals of the core and the sheath and being airtight. a

5. An insulated electric conductor comprising at least one copper core, a surrounding copper sheath, pulverulent mineral insulation separating the core from the sheath, and a layer of an aluminium brass alloy applied to the surface of at least one of the copper parts and being airtight and 'encircling all the exterior of the metal part covered.

FREDERICK WILLIAM TOMLINSON. CHARLES MURRAY BECKE'I'I'. 

